From Roissy Charles de Gaulle airport: take RER B (south direction) to Cité Universitaire (via Paris). You can also use a Car Air France (bus) to Montparnasse, then subway line 4 (south direction) to Porte d’Orléans. Travel duration: 1 hour.

From Orly airport:take an Orlybus bus to Paris, and get out at “Tombe Issoire” (it is the first stop within Paris’ confines). Travel duration: 45 minutes.

From Gare de Lyon train station:take RER A (west direction, end of the line is Cergy-le-Haut) ; change at Châtelet Les Halles ; take RER B (south direction) to Cité Universitaire. You can also take subway line 14 (Saint Lazare direction) ; change at Châtelet ; take subway line 4 to Porte d’Orléans. Travel duration: 45 minutes